Big Brother begins – but does anybody still care?

Tonight, for the ninth year in a row, the presenter Davina McCall will bound enthusiastically on to our television screens to unveil this year's Big Brother contestants, including a Muslim convert, a Thai Buddhist and a reformed gangster who was deported from America.

But who will be watching? And as Channel 4 argues its case for a £150m annual public subsidy, is the ageing reality TV show really the kind of programme it should be making?

Viewing figures for last year's series were the worst ever, averaging just 3.8 million compared with an average of 4.5 million viewers in 2006. And the show has been struck by a series of rows over racism and bullying.

Following the lacklustre performance of Big Brother 8, Endemol, which makes the programme for Channel 4, has attempted to breathe new life into the format. The executive producer Phil Edgar-Jones insisted that this year's contestants are "people with a bit of depth" rather than "screaming wannabes".

He said: "It gets written off every year. It's down to the contestants and the housemates we pick; it almost doesn't matter what twists and turns we introduce. We have got people you might not have seen on any show like this before. These people have got a little more to offer."

There are 16 contestants in the new series – four more than usual – including four housemates with children, three who have been born outside of the UK, one who has had a breast enlargement and a former child actor who appeared in the film Night Train To Venice with Hugh Grant, as well as the first couple to appear on Big Brother.

Phil Mahoney, broadcast account director at the media agency PHD said: "Big Brother is a bit tired, but it's irreplaceable for Channel 4. If they did drop Big Brother, they would miss out on a show that will deliver 4 million viewers a night and bring in younger viewers. They need something big to happen this year." There are still two years left to run on Channel 4's contract with Endemol and Mr Mahoney fully expects to see series 10 and 11. But programme chiefs will be keeping an anxious eye on ratings for tonight's debut.

The contestants

Alexandra, 23, Accounts executive: Single mum. Islam convert who is now non-practising

Jennifer, 22, Part-time model: Full-time mum. Vegetarian against fox-hunting and fur

Kathreya, 30, Massage therapist: Big Brother's first Thai housemate, now a UK citizen

Lisa, 40, Sales rep. One half of the first couple to enter the house. Dating Mario

Rachel, 24, Trainee teacher: A former child actor who starred with Hugh Grant

Rebecca, 21, Nursery nurse: Attention-seeker who wants to be rich and famous

Stephanie, 19, Student: Kicked off Popstars for lying about her age. Now plays guitar in band

Sylvia, 21, Student: Family fled Sierra Leone. Attends church every Sunday

Dennis, 23, Dance studentand teacher: Self-confessed egotist

Dale, 21, Student: Part-time DJ training to be a PE teacher who likes 'fit' girls

Darnell, 26, Songwriter: Born in UK, raised in St Louis but deported for gang crime

Luke, 20, Politics student: Referees wrestling and likes wearing suits from Asda

Mario, 42, Former tag officer at the Home Office: Other half of the first BB couple

Michael, 33, Radio producer: Lost his sight 10 years ago while having operation

Mohamed, 23, Toy demonstrator: Born in Somalia. Wants to win to help family

Rex, 24, Executive chef: London socialite born into a family of restaurateurs